Grease lubricant



United States Patent Ofiiice 3,354,086 Patented Nov. 21, 1967 3,354,086 GREASE LUBRICANT Jerome Panzer, Roselle Park, James Nixon, Elizabeth,

and Rudolph Kassinger, Westfield, N.J., assignors to Esso Research and Engineering Company, a corporation of Delaware No Drawing. Filed May 28, 1964, Ser. No. 371,088

Claims. (Cl. 252-405) This invention relates to lubricants. Particularly, the invention relates to greases thickened with alkaline earth metal salts of acetic acid in combination with other fatty acids, which are improved by including a copolymer of certain unsaturated esters.

Lubricating greases containing alkaline earth metal salts, particularly calcium salts, of acetic acid and various C to C fatty acids, have found wide spread use in commercial applications. In general, these mixed salt lubricants have good antiwear and load-carrying properties, which properties have made them commercially successful. However, greases of this type tend to unduly harden, particularly when used at elevated temperatures, e.g. in the end caps of bearings, and also frequently plug small diameter feed lines of some centralized lubrication systems where the grease is forced under pressure to the parts to be lubricated, particularly when the rate of feed is low and the feed lines are in a hot environment. It has now been found that greases of the foregoing type can be inhibited against hardening and line plugging by certain copolymers of unsaturated esters.

The aforementioned mixed-salt lubricants will generally contain salt of 4 to 25 moles, preferably 5 to 15, moles of acetic acid per molar proportion of C to C higher fatty acid. Greases prepared from the mixed salts usually contain 5 to 40.0 wt. percent, e.g. 15 to 35 Wt. percent, of mixed salt. It has now been found that these mixed salt lubricant systems can be substantially improved with regard to hardening and line plugging by the inclusion of 0.05 to 3.0 wt. percent, preferably 0.1 to 1.0 Wt. percent, of certain copolymers. All of said preceding weight percents are based on the total weight of the composition.

The C to C fatty acid of the mixed salt system in cludes, aliphatic, saturated or unsaturated, unsubstituted, monocarboxylic acids such as capric, caprylic, nonanoic, lauric acid, myristic, palmitic, stearic, arachidic, oleic, ricinoleic, hydrogenated fish oil, tallow acids, etc.

The copolymers used in the invention are those which are soluble in mineral lubricating oil and have Staudinger molecular weights of about 20,000 to 1,000,000, preferably 100,000 to 800,000. These copolymers are formed by copolymerizingz- (A) a monoor diester of a fully esterified C to C aliphatic unsaturated monoor. dicarboxylic acid, e.g. acrylic, methacrylic, fumaric, maleic and itaconic acid,

. and a C to C preferably a C to C saturated, straight or branched chain aliphatic alcohol, (B) an ester of' vinyl alcohol and a C to C saturated aliphatic monocarboxylic acid, and (C) a polar monomer such as 2-N- vinylpyrrolidone, maleic anhydride and hydroxyalkyl acrylate.

saturated carboxylic acids that may be used in this invention include octyl itaconate, octadecyl maleate, lauryl fumarate, lauryl maleate, tallow maleates, oleyl fumarate, allyl fumarate, tallow fumarates, C to C Oxo fumarate. Esters of glycol monoalkyl ethers and fumaric or maleic acids may also be used, as for example, cellosolve fumarate (glycol monoethyl ether fumarate).

By tallow fumarates or maleates is meant the esters of fumaric acid or maleic acid and the alcohols derived by hydrogenation of tallow. The latter are principally C and C alcohols, with minor amounts of C C and C alcohols.

The Oxo alcohols are well known in the art and are prepared from olefins by reaction with carbon monoxide and hydrogen in the presence of a suitable catalyst, e.g. cobalt carbonyl. The reaction products are primarily aldehydes having one more carbon atom than the starting olefins. These aldehydes are then hydrogenated in a separate catalytic stage to convert them to the corresponding alcohols.

Examples of esters of vinyl alcohol include vinyl acetate, vinyl propionate, vinyl n-butyrate, etc.

The hydroxyalkyl acrylates, which can be used as the polar monomer, can be represented by the formula:

wherein: R is selected from the group consisting of hydrogen, methyl, and ethyl radicals; R" is a saturated aliphatic hydrocarbon group of from 2 to 6 carbon atoms; and n is an integer of from 1 to 5, and is preferably 1. Specific examples of such compounds include hydroxyamyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxyethyl methacrylate, 2,3-dihydroxy propyl methacrylate, etc.

The polymers of the present invention may be prepared by various well known polymerization processes, including low temperature Friedel-Crafts polymerization, ionic polymerization processes, or radiation polymerization processes. Free radical catalysts, for example peroxidetype catalysts are particularly useful. These catalysts include benzoyl peroxide, acetyl peroxide, urea peroxide, and tertiary butyl perbenzoate. A hydroperoxide or an azo catalyst such as alpha, alpha-azo-bis-isobutyronitrile may be used. The polymerization can be carried out in a suitable inert solvent such as benzene, heptane, mineral oil, etc. in order to better control the reaction velocity and molecular weight. Oxygen can be excluded during the polymerization by the use of a blanket of an inert gas such as nitrogen or carbon dioxide. The molecular weight of the polymer can be determined by measuring the viscosity of a solution containing 5 milligrams of the copolymer per cc. of diisobutylene and applying the Staudinger equation. At the termination of the polymerization the polymer can be stripped of any unconverted monomer.

The lubricating oilused in the compositions of the invention may be either a mineral lubricating oil or a synthetic lubricating oil, although the mineral oils are preferred.

. Various other additives may also be added to the lubrieating composition in amounts of 0.1 to 10.0 weight percent each. Such additives include oxidation inhibitors such as phenyl-alpha-naphthylamine, phenyl-beta-naphthylamine; corrosion inhibitors such as sorbitan monooleate, sodlum mtrite; dyes; grease thickeners; and the like.

The lubricants of the invention can be formed in a number of different Ways. The most convenient way is to neutralize the acids with metal base in oil and in the presence of the polymer. It is believed that the polymer acts on the salt particles formed by the neutralization to inhibit their subsequent aggregation and to result in a better dispersion of the salts. Usually, after neutralizing,

the resulting composition will be heated to about 225 F.

to 600 F., preferably 275 F. to 350 F. to dehydrate the composition. I I

:about 500,000 and contained 0.394 molar EXAMPLE I A grease thickened with the mixed salts of acetic acid and tallow :fatty acid in a relative molar ratio of 10 to 1 was prepared as follows:

7.7 parts of tallow fatty acid, 0.6 parts of a polymer solution consisting of 37 Wt. percent polymer and 63 wt. percent inert mineral lubricating oil, and 11.4 parts of hydrated lime was added to 63.1 parts of mineral lubricating oil of 80 SUS. viscosity at 210 F. in an electrically heated grease kettle. This mixture was warmed, while .stirring, to 125 F. 16.2 parts of glacial acetic acid was slowly added to the kettle. The temperature of the kettle contents was then raised to about 300 F. for about 15 minutes in order to dehydrate the grease. The grease was then cooled to 275 E, where 1 part of phenyl-beta-naph- .thylamine was added'as an oxidation inhibitor. The grease was further cooled to 100 F. and homogenized by passage through a Morehouse mill having 0.003" clearance.

The tallow fatty acid (beef tallow acid) had a Saponification No. of about 195, and Iodine number (Wijs) of about 55 and averaged about a C chain.

The polymer used above had a molecular Weight of proportion of =di-tallow fumarate, 0.424 molar proportion of di-C Oxo fumarate and 0.131 molar proportion of hydroxyethyl methacrylate per molar proportion of vinyl acetate. The polymer was made by copolymerizing a mixture of the monomers in a mineral oil diluent under a nitrogen atmosphere using tertiary butyl perbenzoate as the catalyst and using about 115% excess vinyl acetate. This excess vinyl acetate was evaporated by nitrogen purging at the end of the polymerization reaction. The resulting product consisted of about 37 wt. percent polymer dissolved in 63 Wt. percent mineral lubricating oil diluent.

The hydroxyethyl methacrylate used above had the structure:

A comparison grease (Grease A) was prepared in the same manner as the grease of Example I, except for different proportions and the fact that no polymer was used.

.The formulations and properties of the greases of Example I and the comparison Grease A are summarized in the following table:

TABLE Composition, Wt. Percent Example I Grease A Glacial Acetic Acid. 16. 2 19. Hydrated Lnne 11. 4 13. 8 Tallow Fatty Acid. 7. 7 10. 0 Phenyl-beta-naphthylamine 1. 0 i 1. 0 Polymer .Solution 0. 6 Mineral Lubricating Oil, 80 SUSat 210? F... 63. 1 56. 2 Properties:

ASTM Penetration, 77 F., mm.l10, 60

strokes 335 325 Trabon'Liie, Hrs 400 1 237 Hardening-Micro-cone Penetration,

ASTM D-1403, 5ST;

Room temperature:

Initial 174 186 Percent A pen. after 1 day 12. 6 21.5 150 F.:

Percent A pen, after 1 day 19. 5 33. 9 Percent A pen. after 1 week 31. 0 43. 5 Dispensability at 0 F., 150 p.s.i. No. 1

ea illary, grams/min;

'tial 0. 85 1. 00 After 16 hrs. at 300 F 0.35 02. 4 Percent reduction in flow rate 59 76 37 wt. percent polymer in 63 wt. percent oil.

The Trabon life was determined in a Trabon centralized lubrication system which included a pump circulating the grease from a reservoir under high pressure through small diameter feed tubes and back to the reservoir. The number 'of hours of operation before plugging of the system was determined.

The hardening information was determined simply by measuring the percent change in micro-cone penetration. For example, the grease of Example I had an initial microcone penetration of 174 but after standing 1 day (24 hours) its penetration had decreased to 152 or a change of 12.6%.

The dispensability at 0 F., under p.s.i. through a capillary opening was-determined by a test procedure described in an article on page 76, et seq. in the February 1963 issue of Lubrication Engineering.

As seen by the preceding table, the grease composition of the invention (Example 1) containing 0.6% of the copolymer solution, i.e. 0.22 wt. percent polymer, showed less susceptability to line plugging and hardening than the comparison Grease A of a comparable ASTM penetration but which contained no polymer. This is indicated by the longer Trabon life, the lesser percent change in penetration in the Micro-cone Penetration test, the greater lubricator cup delivery rate and the lesser percent reduction in flow rate through a No. 1 capillary. While Grease A varied somewhat from the grease of Example I with regard to the proportions of materials used, it can be seen from their ASTM penetrations that both greases were made up to substantially the same consistencies. Apparently, the polymer also increases the yield, i.e. the hardness of the grease, perhaps by more finely dispersing the calcium salts. Thus, with the polymer present, the grease of Example I had substantially the same ASTM consistency .as Grease A even though it contained less of the calcium salt thickener. Since the thickener is the more expensive part of the grease, it is an economic advantage to obtain thickening to the desired consistency with the minimum amount of thickener, thus representing another advantage for using the polymer.

While the data of the table has shown hardening inhibition when using the polymer of the invention, several other polymers including polyethylene, and the copolymer of ethylene and vinyl acetate were found either ineffective or not as effective as the copolymer of the invention.

As a further example of the invention, Example I can be repeated exactly but using a polymer containing 0.131 molar proportion of 2-N-viny1 pyrrolidone as the polar monomer in place of the 0.131 molar proportion of hydroxyethyl methacrylate used in Example I.

As yet another example of the invention, Example I can be repeated exactly but using a polymer containing 0.131 molar proportion of maleic anhydride as the polar monomer in place .of the 0.131 molar proportion of hydroxyethyl methacrylate used in Example I.

What is claimed is:

1. A lubricating grease composition comprising a major amount of lubricating oil, about 5 to 40 wt. percent of calcium mixed salts of about 4 to 25 moles of acetic acid per mole of C to C fatty acid, and as an inhibitor against hardening about 0.05 to 3.0 wt. percent of an oilsoluble polymer having a molecular weight of about 20,000 to 1,000,000 consisting essentially of: (A) a fully esterified ester of a C to C saturated aliphatic alcohol and a C to C aliphatic unsaturated carboxylic acid :having 1 to 2 carboxylic acid groups, (B) an ester of vinyl alcohol and a C to C saturated aliphatic monocarboxylic acid and (C) a polar monomer selected from the group consisting of 2-N-vinyl pyrrolidone, maleic anhydride, and hydroxyalkyl acrylates of the formula:

R o CHz=G-i JOR-(OH)D where R is selected from the group consisting of hydrogen and C to C alkyl groups, R" is a saturated aliphatic hydrocarbon group of 2 to 6 carbon atoms and n is 1 to 5, said copolymer being formed of about 0.1 to 2 molar proportions of ester of said C to C carboxylic acid, and

about 0.1 to 0.5 molar proportions of said molar monomer per molar proportion of said vinyl alcohol ester and wherein said mixed salts are prepared in situ by neutralization of said acetic and C to C fatty acids with alkaline earth metal base in at least a portion of said lubricating oil and in the presence of said oil soluble polymer.

2. A grease according to claim 1, wherein said polymer has a molecular weight of 100,000 to 800,000 and is a polymer of tallow fumarate, vinyl acetate and said hydroxyalkyl acrylate.

3. A grease according to claim 2, wherein the amount of said polymer is 0.1 to 1.0 wt. percent.

4. A lubricating grease comprising a major amount of mineral lubricating oil and about 15 to 35 wt. percent of calcium mixed salts of acetic acid and C to C fatty acid in a molar proportion of about 5 to 15 moles of acetic acid per molar proportion of C to C fatty acid, and as an inhibitor against hardening about 0.1 to 1.0 Wt. percent of an oil-soluble polymer having a molecular weight of about 100,000 to 800,000 consisting essentially of: (A) diester of C to C saturated aliphatic alcohol and fumaric acid, (B) vinyl acetate and (C) hydroxyalkyl acrylate of the formula:

wherein R is a C to C alkyl group and R is a saturated aliphatic hydrocarbon group of 2 to 6 carbon atoms, said polymer containing about 0.2 to 1.0 molar proportions of said diester and about .03 to .3 molar proportions of said hydroxyalkyl acrylate per molar proportion of said vinyl acetate, and wherein said calcium mixed salts are formed in situ by neutralization of said acetic and C to C fatty acid in at least a portion of said oil and in the presence of said polymer.

5. A grease according to claim 4, wherein said hydroxyalkyl acrylate is hydroxyethyl methacrylate.

References Cited UNITED STATES PATENTS 3,083,159 3/1963 Clark et a1 252--51.5 3,083,163 3/1963 Perrus 25240.5 3,137,679 6/1964 Agius et al. 252-56 DANIEL E. WYMAN, Primary Examiner. I. VAUGHN, Assistant Examiner. 

1. A LUBRICATING GREASE COMPOSITION COMPRISING A MAJOR AMOUNT OF LUBRICATING OIL, ABOUT 5 TO 40 WT. PERCENT OF CALCIUM MIXED SALTS OF ABOUT 4 TO 25 MOLES OF ACETIC ACID PER MOLE OF C6 TO C30 FATTY ACID, AND AS AN INHIBITOR AGAINST HARDENING ABOUT 0.05 TO 3.0 WT. PERCENT OF AN OILSOLUBLE POLYMER HAVING A MOLECULAR WEIGHT OF ABOUT 20,000 TO 1,000,000 CONSISTING ESSENTIALLY OF: (A) A FULLY ESTERIFIED ESTER OF A C1 TO C20 SATURATED ALIPHATIC ALCOHOL AND A C3 TO C4 ALIPHATIC UNSATURATED CARBOXYLIC ACID HAVING 1 TO 2 CARBOXYLIC ACID GROUPS, (B) AN ESTER OF VINYL ALCOHOL AND A C2 TO C6 SATURATED ALIPHATIC MONOCARBOXYLIC ACID AND (C) A POLAR MONOMER SELECTED FROM THE GROUP CONSISTING OF 2-N-VINYL PYRROLIDONE, MALEIC ANHYDRIDE, AND HYDROXYALKYL ACRYLATES OF THE FORMULA: 